Historically, robot touch sensors are incorporated into a robot bumper assembly. Such bumper assemblies are rigid, movable bumpers that are spaced away and suspended from the robot chassis. Typically, such bumpers include a rigid outer shell suspended from the robot chassis by a series of hardware, such as pivots/bumper arms and coil springs. The springs absorb the impact energy, but require a high impact force, i.e., require that the bumper deflect by several millimeters to absorb the energy before triggering a switch to indicate that an impact event has occurred. The deflection of the rigid bumper relative to the robot's rigid chassis not only requires a swept volume to actuate, but creates visual seams and pinch points on the exterior. The use of the arms and springs require a number of moving parts that create mechanical mounting complexities and can lead to mechanical failure. The distance between the bumper and the robot creates a space in which dust and debris can collect.
Detecting the location of the impact is limited by the number of switches and suspension points that economically can be incorporated into the robot's mechanical geometry. For many robots, two switches, a left switch and a right switch, are used. At best, this allows for three detection zones, right, left, and center if both switches are triggered. The geometrical limitations in using such switches prevent the ability of the robot to detect when it is receiving pressure from above, such as in a wedging situation. Similarly, the robot cannot determine the degree or force of impact.
An alternative bumper design that does not employ complex mechanical mounting, utilizes carbon puck type contacts positioned around a front portion of the robot. Such a structure has several drawbacks. For example, the weight of the carbon puck bumper structure is heavy and changes the center of gravity of the robot. Additionally, the carbon puck bumper structure is expensive to manufacture and the appearance of the bumper is not uniform, making it less than aesthetically pleasing to a consumer.